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void setup() { Serial.begin(115200); timer1 = timerBegin(0, 80, true); timerAttachInterrupt(timer1, &onTimer1, true); // Configura o Timer 1 para o primeiro disparo timerAlarmWrite(timer1, 5000000, false); timerAlarmEnable(timer1); // setupTimer1(); }

DeepBlue

deepbluembedded.com › home › blog › esp32 timers & timer interrupt tutorial (arduino ide)

ESP32 Timers & Timer Interrupt Tutorial (Arduino IDE) – DeepBlueMbedded

February 17, 2025 - /* * LAB: 25 * Name: ESP32 Timer Interrupt Example * Author: Khaled Magdy * For More Info Visit: www.DeepBlueMbedded.com */ #define LED 21 hw_timer_t *Timer0_Cfg = NULL; void IRAM_ATTR Timer0_ISR() { digitalWrite(LED, !digitalRead(LED)); } void setup() { pinMode(LED, OUTPUT); Timer0_Cfg = timerBegin(0, 80, true); timerAttachInterrupt(Timer0_Cfg, &Timer0_ISR, true); timerAlarmWrite(Timer0_Cfg, 50000, true); timerAlarmEnable(Timer0_Cfg); } void loop() { // Do Nothing!

Discussions

Hardware Timer ESP32 Dev Module

Nano ESP32 category you chose is only used for discussions directly related to the Arduino Nano ESP32 board · In the future, please take the time to pick the forum category that best suits the subject of your question. There is an "About the _____ category" topic at the top of each category ... More on forum.arduino.cc

forum.arduino.cc

July 19, 2024

ESP32 hardware timer. Can anyone explain why one code works and the other don't?

This code works: #define LED 2 hw_timer_t *blinkTimer = NULL; volatile bool toggle=0; volatile bool flip=0; void IRAM_ATTR blink(){ toggle=!toggle; if (toggle){ // controversial if statement timerAlarmWrite(blinkTimer, 500000, true); } else if (!toggle){ timerAlarmWrite(blinkTimer, 1500000, ... More on forum.arduino.cc

forum.arduino.cc

August 26, 2023

timer - hw_timer_t, timerAttachInterrupt, portENTER_CRITICAL etc... not defined for ESP8266 - Stack Overflow

I have an ESP8266 NodeMCU 12E development board. I'm trying to implement an ISR that uses a hardware timer as described by this blog here. The blog post was originally meant for ESP32 and it prov... More on stackoverflow.com

stackoverflow.com

Hardware timer, how to run once and restart again?

I had some trouble with timers and alarms on my esp32 doit devboard. Spent many hours trying to debug, end of the days its a silicon issue with the REV0 chips. Not sure if this applies to you but more information can be found here: https://github.com/espressif/arduino-esp32/issues/1313 More on reddit.com

r/esp32

April 12, 2021

Espressif Docs

espressif-docs.readthedocs-hosted.com › projects › arduino-esp32 › en › latest › api › timer.html

Timer — Arduino-ESP32 2.0.14 documentation

"); Serial.print(isrCount); Serial.print(" at "); Serial.print(isrTime); Serial.println(" ms"); } // If button is pressed if (digitalRead(BTN_STOP_ALARM) == LOW) { // If timer is still running if (timer) { // Stop and free timer timerEnd(timer); timer = NULL; } } }

Arduino Forum

forum.arduino.cc › projects › programming

Hardware Timer ESP32 Dev Module - Programming - Arduino Forum

July 19, 2024 - #include #include hw_timer_t *timer = NULL; const int ledPin = 2; void IRAM_ATTR onTimer() { // Toggle LED state digitalWrite(ledPin, !digitalRead(ledPin)); } void setup() { pinMo…

Luis Llamas

luisllamas.es › inicio › tutoriales arduino › curso esp8266 / esp32

How to use ESP32 timers

November 25, 2024 - hw_timer_t *timer = NULL; volatile void has_expired = false; void IRAM_ATTR timerInterrupt() { has_expired = true; } void setup() { Serial.begin(9600); pinMode(LED_BUILTIN, OUTPUT); timer = timerBegin(0, 80, true); // Timer 0, clock divisor 80 timerAttachInterrupt(timer, &timerInterrupt, true); // Attach the interrupt handling function timerAlarmWrite(timer, 1000000, true); // Interrupt every 1 second timerAlarmEnable(timer); // Enable the alarm } void loop() { if(has_expired) { // Tasks to perform when the Timer interrupt is activated digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN)); // Toggle the state of the LED has_expired = false; } }

ESP32 Forum

esp32.com › viewtopic.php

Timer ISR - ESP32 Forum

February 17, 2017 - Here is an example timer sketch, ... = true timerAlarmWrite(timer, 1000000, true); //1000 ms timerAlarmEnable(timer); } void endTimer() { timerEnd(timer); timer = NULL; } void setup() { Serial.begin(115200); startTimer(); } void loop() {} ... The maximum sampling frequency of 6000 times a second can be found here ... https://esp32.com/viewtopic.php?f=2&t=1075 If I may ask, what kind of project needs to sample an analog input at more than 6000 times a second? Free book on ESP32 ...

ElectronicWings

electronicwings.com › esp32 › esp32-timer-interrupts

ESP32 Timer Interrupts | ESP32

/* Timer Interrupt in ESP32, Alarm generation in ESP32 www.electronicwings.com */ #define LED_PIN 2 // In some ESP32 board have inbuilt LED volatile int interruptCounter; //for counting interrupt int totalInterruptCounter; //total interrupt counting int LED_STATE=LOW; hw_timer_t * timer = NULL; //H/W timer defining (Pointer to the Structure) portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED; void IRAM_ATTR onTimer() { //Defining Inerrupt function with IRAM_ATTR for faster access portENTER_CRITICAL_ISR(&timerMux); interruptCounter++; portEXIT_CRITICAL_ISR(&timerMux); } void setup() { Serial.begin(115200); pinMode (LED_PIN, OUTPUT); timer = timerBegin(0, 80, true); // timer 0, prescalar: 80, UP counting timerAttachInterrupt(timer, &onTimer, true); // Attach interrupt timerAlarmWrite(timer, 1000000, true); // Match value= 1000000 for 1 sec.

Upsy

upesy.com › tutorials › esp32 › esp32 programming › arduino code › basics › timers

Timer ESP32 with Arduino Code: Master the time - uPesy

February 2, 2023 - hw_timer_t * timer = NULL; void IRAM_ATTR timer_isr() { // This code will be executed every 1000 ticks, 1ms } void setup() { Serial.begin(115200); uint8_t timer_id = 0; uint16_t prescaler = 80; // Between 0 and 65 535 int threshold = 1000000; // 64 bits value (limited to int size of 32bits) timer = timerBegin(timer_id, prescaler, true); timerAttachInterrupt(timer, &timer_isr, true); timerAlarmWrite(timer, threshold, true); timerAlarmEnable(timer); } void loop() { }

CircuitDigest

circuitdigest.com › microcontroller-projects › esp32-timers-and-timer-interrupts

ESP32 Timers & Timer Interrupt Tutorial

August 5, 2025 - void setup() { pinMode(LED, OUTPUT) My_timer = timerBegin(0, 80, true); timerAttachInterrupt(My_timer, &onTimer, true); timerAlarmWrite(My_timer, 1000000, true); timerAlarmEnable(My_timer); } void loop() { }

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ESP32 Forum

esp32.com › viewtopic.php

repetitive timerAlarmWrite problem? - ESP32 Forum

December 18, 2020 - But seriously read about freeRTOS ... running freeRTOS on a ESP32. ... Thank you. I will investigate the rtos timer. I am not sure but I think its maximum resolution is 1microsecond. This could not be enough for higher micro-stepping settings and for some thread pitches. I tried to put that code into the loop, but the problem still persists. Actually, I don't think the problem is that the encoder isr is too busy. Even with the frequency update code in the loop, the timerAlarmWrite function called ...

Phatiphat Thounthong

phatiphatt.wordpress.com › watchdog-timer-esp32

Watchdog Timer (ESP32) – Phatiphat Thounthong

October 2, 2019 - //setup Watchdog Timer watchdogTimer = timerBegin(myTimerWDT, 80, true); timerAlarmWrite(watchdogTimer, 2000000, false); timerAttachInterrupt(watchdogTimer, &interruptReboot, true); timerAlarmEnable(watchdogTimer); //End setup WDT

Arduino Forum

forum.arduino.cc › projects › programming

ESP32 hardware timer. Can anyone explain why one code works and the other don't? - Programming - Arduino Forum

August 26, 2023 - This code works: #define LED 2 hw_timer_t *blinkTimer = NULL; volatile bool toggle=0; volatile bool flip=0; void IRAM_ATTR blink(){ toggle=!toggle; if (toggle){ // controversial if statement timerAlarmWrite(blinkTimer, 500000, true); } else if (!toggle){ timerAlarmWrite(blinkTimer, 1500000, ......

Phatiphat Thounthong

phatiphatt.wordpress.com › esp32-sampling_mode

ESP32 Timer Interrupt (Sampling Mode) – Phatiphat Thounthong

October 21, 2020 - //Step #3 timerAlarmWrite(My_timer, 2000000, true); //timerAlarmWrite(timer?, Sampling Time, bool autoreload); //Sampling Time=> 2 s = 2000000/(80,000,000 MHz/prescale 80) //autoreload: if it is true, timer will repeat.

ESP32 Forum

esp32.com › viewtopic.php

Timers and interrupts not working as expected - ESP32 Forum

January 12, 2024 - hw_timer_t * timer = NULL; void IRAM_ATTR onTimer() { bool state = digitalRead(5); digitalWrite(5, !state); } void setup() { pinMode(5, OUTPUT); Serial.begin(115200); timer = timerBegin(0, 80, true); // Timer 0, prescaler 80, count up timerAttachInterrupt(timer, &onTimer, true); timerAlarmWrite(timer, 100, true); timerAlarmEnable(timer); timerWrite(timer, 50); } void loop() { }

Stack Overflow

stackoverflow.com › questions › 54602398 › hw-timer-t-timerattachinterrupt-portenter-critical-etc-not-defined-for-esp8

timer - hw_timer_t, timerAttachInterrupt, portENTER_CRITICAL etc... not defined for ESP8266 - Stack Overflow

Top answer

1 of 1

They're not defined because they're in the ESP32 SDK, which is completely separate (different CPU, different instruction set, different OS) from the ESP8266. Documentation about the ESP32 won't apply to the ESP8266.

Take a look at the ESP8266 "NONOS SDK" - this is the "OS" that the ESP8266 Arduino SDK is built on. It includes calls for hardware timers (hw_timer_init(), hw_timer_arm(), hw_timer_set_func()). You can find the documentation for it here.

Beware, there's also a "Free RTOS" for the ESP8266. When you're searching for example code, people are often not clear about whether their code is for the NONOS SDK or the Free RTOS SDK.

Free RTOS a separate piece of software; you won't be able to use its functions in an Arduino SDK program. Some people have gotten parts of the Arduino SDK running with it but that's a deep rabbit hole that can waste a lot of your time. If you decide to go that route you're better off abandoning the Arduino SDK calls and just writing a proper FreeRTOS program.

QuadMeUp

blog.quadmeup.com › home › programming › esp32, arduino and timer/alerts

ESP32, Arduino and Timer/Alerts » QuadMeUp

May 20, 2025 - One tick of the timer is 1us timer = timerBegin(0, 80, true); //Set the handler for the timer timerAttachInterrupt(timer, &onTimerHandler, true); // How often handler should be triggered? 1000 means every 1000 ticks, 1ms timerAlarmWrite(timer, 1000, true); //And enable the timer timerAlarmEnable(timer); } void loop() { //Here you can do whatever you want }

reddit.com › r/esp32 › hardware timer, how to run once and restart again?

r/esp32 on Reddit: Hardware timer, how to run once and restart again?

April 12, 2021 -

Guys

I have a DevKitC dev board, and I'm trying to set up a HW timer that I want to re-use under certain conditions. In other words, I don't want it to reload automatically, it should run once and then remain dormant until I enable it again. It seems to work the first time, but when I enable the timer a second time it fires immediately, without any delay. It seems I'm not resetting it properly, so that the counter starts from 0 again (?).

What I've tried is this:

initialize timer 0 in setup(), with a prescaler for 80MHz.

myTimer = timerBegin (0, 80, true);
timerAttachInterrupt (myTimer, &isrMyTimer, true);

then when I want to use the timer I enable it as follows (for a duration of 3 seconds):

timerAlarmWrite(myTimer, 3000000), false);
timerAlarmEnable(myTimer);

I am also trying to confirm the frequency to use for the timer, whether it is indeed 80MHz. I get the values as shown below for the different functions. Any thoughts on what they mean?

getCpuFrequencyMhz()		240	
getXtalFrequencyMhz()		40
getApbFrequency()		80000000

Top answer

1 of 4

2 of 4

I managed to get it working. The trick that worked for me was to reset the timer (counter) before each use, with the following statement: timerRestart() Below is a little pseudo sketch, only showing the relevant statements, to give you or anyone finding this post later, an idea of what worked for me. #include // only needed to get ESP32 frequency detail hw_timer_t * tmrTEST = NULL; // timer used for TESTING unsigned long lngTimerStart = 0; // system micro-seconds at timer start int tmrDuration = 5; // run timer for 5 seconds // Interrupt Service Routine called when TEST timer fires. void IRAM_ATTR isrTimerTEST() { Serial.print(" >>>>> TEST TIMER ISR: "); Serial.print( micros() ); Serial.print(" diff="); Serial.println((micros()-lngTimerStart)/1000/1000); } void setup() { Serial.begin(115200); ... // Set up TEST timer.. tmrTEST = timerBegin (1, 80, true); // use ESP32 Timer 1, pre-scale 80 (for 80MHz freq), count up. timerAttachInterrupt (tmrTEST, &isrTimerTEST, true); // attach the function to call when timer interrupt fires. Edge. Serial.print(" >> CPU Freq: "); Serial.println(getCpuFrequencyMhz()); Serial.print(" >> XTL Freq: "); Serial.println(getXtalFrequencyMhz()); Serial.print(" >> APB Freq: "); Serial.println(getApbFrequency()); ... } void loop() { ... if (tmrDuration > 0) { // initiate TEST timer. duration in micro-seconds. False to run once. timerAlarmWrite(tmrTEST, (tmrDuration * 1000000), false); timerRestart(tmrTEST); // reset timer counter timerAlarmEnable(tmrTEST); // start the timer lngTimerStart = micros(); Serial.print(" >>>>> TimerTEST dur="); Serial.print(tmrDuration); Serial.print(" start: "); Serial.println( lngTimerStart ); } ... } Thanks for your replies and time !

reddit.com › r/esp32 › timer error building infinity cube. new syntax?

r/esp32 on Reddit: Timer error building infinity cube. New syntax?

June 8, 2025 -

Building, https://github.com/mecharms/Infinity-LED-CUBE/tree/main

I believe the problem is the timer is written under old format so does not work with new version in IDE.

Does anyone know if this is just a syntax fix?

 //--------------------------------
  // Configure Prescaler to 80, as our timer runs @ 80Mhz
  // Giving an output of 80,000,000 / 80 = 1,000,000 ticks / second
  timer = timerBegin(0, 80, true);                
  timerAttachInterrupt(timer, &onTime, true);    
  // Fire Interrupt every 1m ticks, so 1s
  timerAlarmWrite(timer, 5000000, true);      
  timerAlarmEnable(timer);
  //--------------------------------

C:\Users\Jason\Downloads\Infinity-LED-CUBE-main\Infinity-LED-CUBE-main\code\cube_led\cube_led.ino: In function 'void setup()':

C:\Users\Jason\Downloads\Infinity-LED-CUBE-main\Infinity-LED-CUBE-main\code\cube_led\cube_led.ino:3829:21: error: too many arguments to function 'hw_timer_t* timerBegin(uint32_t)'

3829 | timer = timerBegin(0, 80, true);

| ~~~~~~~~~~^~~~~~~~~~~~~

In file included from C:\Users\Jason\AppData\Local\Arduino15\packages\esp32\hardware\esp32\3.2.0\cores\esp32/esp32-hal.h:98,

from C:\Users\Jason\AppData\Local\Arduino15\packages\esp32\hardware\esp32\3.2.0\libraries\Wire\src/Wire.h:33,

from C:\Users\Jason\Downloads\Infinity-LED-CUBE-main\Infinity-LED-CUBE-main\code\cube_led\cube_led.ino:2:

C:\Users\Jason\AppData\Local\Arduino15\packages\esp32\hardware\esp32\3.2.0\cores\esp32/esp32-hal-timer.h:35:13: note: declared here

35 | hw_timer_t *timerBegin(uint32_t frequency);

| ^~~~~~~~~~

C:\Users\Jason\Downloads\Infinity-LED-CUBE-main\Infinity-LED-CUBE-main\code\cube_led\cube_led.ino:3830:23: error: too many arguments to function 'void timerAttachInterrupt(hw_timer_t*, void (*)())'

3830 | timerAttachInterrupt(timer, &onTime, true);

| ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

C:\Users\Jason\AppData\Local\Arduino15\packages\esp32\hardware\esp32\3.2.0\cores\esp32/esp32-hal-timer.h:50:6: note: declared here

50 | void timerAttachInterrupt(hw_timer_t *timer, void (*userFunc)(void));

| ^~~~~~~~~~~~~~~~~~~~

C:\Users\Jason\Downloads\Infinity-LED-CUBE-main\Infinity-LED-CUBE-main\code\cube_led\cube_led.ino:3832:3: error: 'timerAlarmWrite' was not declared in this scope; did you mean 'timerWrite'?

3832 | timerAlarmWrite(timer, 5000000, true);

| ^~~~~~~~~~~~~~~

| timerWrite

C:\Users\Jason\Downloads\Infinity-LED-CUBE-main\Infinity-LED-CUBE-main\code\cube_led\cube_led.ino:3833:3: error: 'timerAlarmEnable' was not declared in this scope; did you mean 'timerAlarm'?

3833 | timerAlarmEnable(timer);

| ^~~~~~~~~~~~~~~~

| timerAlarm

exit status 1

Compilation error: too many arguments to function 'hw_timer_t* timerBegin(uint32_t)'

Thank you!

Top answer

1 of 3

That library hasn't been updated for Arduino 3.0. This is the old way to make timers: prescaler=80000000/frequency; timer = timerBegin(0, prescaler , true); timerAttachInterrupt(timer, &onTick, true); timerAlarmWrite(timer, 1, true); timerAlarmEnable(timer); and this is the new way, where 'frequency' is in Hz. timer = timerBegin(frequency); timerAttachInterrupt(timer, &onTick); timerAlarm(timer, 1, true, 0);

2 of 3

You can download and use older versions of the Arduino framework that builds. The last minor update for that version should still build.

reddit.com › r/esp32 › working interrupt timer example?

r/esp32 on Reddit: Working interrupt timer example?

March 26, 2024 -

I'm using platformio (6.1.14) and Arduino. My code compiles just fine in the Arduino IDE but as soon as I use platformIO it breaks apart, despite having worked before.

I have been using ESP32TimerInterrupt.

The error message is ".pio/libdeps/myESP32/ESP32TimerInterrupt/src/ESP32TimerInterrupt.hpp:347:23: error: 'TIMER_BASE_CLK' was not declared in this scope". This error happens during the include. So nothing in my code. checking through the library indeed the TIMER_BASE_CLK is not defined.

Other examples require the usage of timerAlarmWrite() which gives me 'timerAlarmWrite' was not declared in this scope.

Now i'm happy to just switch to a different way of implementing an interrupt timer but i can't seem to find a working example and everything i'm finding is either missing the TIMER_BASE_CLK definition or won't work for other reasons.
Happy to take any pointers

Top answer

1 of 1

My guess is PlatformIO's ESP-IDF package isn't as new as the one in Arduino IDE, which always has the latest espressif bits, unlike PIO. Without seeing your code I can't really say much.

Arduino Forum

forum.arduino.cc › projects › programming

ESP32 Timer Interrupt - Programming - Arduino Forum

June 10, 2024 - Hi Folks, I am using Esp32 Dev Module to develop the timer interrupt code .but when I am using timerBegin() function I am getting errors like that: timerBegin() function can accept only one argument.Please help me out t…